JP2010209937A - Contact type mechanical seal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contact type mechanical seal suppressing a decline in flatness as the whole sealing end face, even if the pressure of a fluid to be sealed is high. <P>SOLUTION: The contact type mechanical seal provided in an annular space 3 formed between the inner peripheral surface 4a of a shaft sealing part casing 4 and a rotating shaft 2, includes a rotating seal ring 22 relatively rotated by the rotation of the rotating shaft 2, and a static seal ring 24. The fluid is sealed by the contact between the first sealing end face 26 of the rotating seal ring 22 and the second sealing end face 27 of the static seal ring 24, and the static seal ring 24 is distorted more easily than the rotating seal ring 22 under the pressure of the fluid. Cross-sectional change parts 37 causing concentrated distortion are arranged equally in the circumferential direction on a circumferentially continuous surface part other than the second sealing end face 27 out of the static seal ring 24. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a contact-type mechanical seal that seals fluid by bringing the sealing end surfaces of a pair of relatively rotating sealing rings into contact with each other.

For example, as a sealing device incorporated in a rotary device such as an industrial process pump or a mixer in which a volatile liquid is sealed, there is one having a pair of mechanical seals on a primary side and a secondary side ( Patent Document 1). A set of the primary side and the secondary side prevents the gas generated by the vaporization of the process liquid inside the rotating equipment from leaking to the atmosphere side.
The mechanical seal described in Patent Document 1 has a rotary sealing ring attached to the rotating shaft side and a stationary sealing ring attached to the casing side, and includes a sealing end face of the rotating sealing ring and a sealing end face of the stationary sealing ring. Prevents gas (fluid) leakage.

JP 2006-83889 A (see FIG. 1)

In the mechanical seal described in Patent Document 1, since the rotary seal ring is made of a hard material such as ceramics, even if the fluid to be sealed becomes high pressure, distortion that adversely affects the sealed end face hardly occurs. However, since the stationary seal ring is made of a relatively easily deformable material such as carbon, it is more likely to be deformed than a rotary seal ring at a high pressure.
Further, the stationary seal ring is held by a retainer fixed to the casing so as to be movable in the axial direction via a spring. For this reason, the stationary seal ring is not fixed to the casing or the retainer, and has a structure that is more easily deformed than the rotary seal ring.

For this reason, when the pressure of the fluid to be sealed is increased, the stationary sealing ring may be deformed and a large distortion (swell) may be generated in the sealing end face, and this distortion is not uniform in the entire circumferential direction of the sealing end face, and is not localized. In some cases, a greatly distorted portion is generated discontinuously. In this case, the flatness of the entire sealing end face of the stationary sealing ring and the parallelism with respect to the sealing end face of the rotating sealing ring which is a contact partner are impaired.
If the flatness of the sealing end surface of the stationary sealing ring is impaired, the sealing end surface cannot be maintained in an appropriate contact state, the sealing function is deteriorated, and fluid leakage may occur.

  Accordingly, an object of the present invention is to provide a contact-type mechanical seal that can suppress a decrease in flatness as a whole sealing end surface even when a fluid to be sealed becomes high pressure.

  The contact-type mechanical seal of the present invention is provided in an annular space formed between an inner peripheral surface of a casing and a rotary shaft coaxial with the inner peripheral surface, and is relatively rotated by the rotation of the rotary shaft. One sealing ring and a second sealing ring, and the first sealing end surface of the first sealing ring and the second sealing end surface of the second sealing ring come into contact with each other on one side in the axial direction of the space portion. A contact-type mechanical seal that seals a fluid and has a configuration in which the second sealing ring is more likely to be distorted than the first sealing ring by pressure of the fluid, and the second sealing ring in the second sealing ring The cross-section changing portions that can cause intensive strain are arranged uniformly in the circumferential direction on the surface portion that is continuous with the circumferential direction except for the end face.

According to the present invention, when the fluid is sealed, if the second sealing ring is distorted by the pressure of the fluid, the cross-sectional change provided in the surface portion continuous in the circumferential direction of the second sealing ring. In addition, intensive strain (concentrated stress) can be positively generated in the portion, and the cross-section changing portions are arranged uniformly in the circumferential direction, so that the portion where intensive strain is generated It can be made to continue at equal intervals in the circumferential direction. For this reason, the whole 2nd sealing end surface of a 2nd sealing ring can be corrected to the surface where the same or substantially the same uneven | corrugated distortion pattern continues in the circumferential direction. That is, only a part of the second sealing end surface in the circumferential direction can be prevented from being greatly deformed locally, and the flatness as the entire second sealing end surface and the parallelism with respect to the counterpart first sealing end surface Can be suppressed.
In addition, as said cross-section change part, it can be set as the recessed part group which consists of a single recessed part, the several recessed part provided closely, etc., for example.

  The contact-type mechanical seal has a cylindrical boss portion that is located radially inward of the second sealing ring and guides the movement of the second sealing ring toward the first sealing ring, An annular retainer fixed to the casing; an elastic member that urges the second sealing ring toward the first sealing ring and presses the second sealing end face against the first sealing end face; and the second sealing ring; A seal ring that is provided between the boss portion and seals between the two, and the second seal ring includes a tip side seal ring on which the second seal end face is formed, and the tip side A base-side seal ring that is a separate body from the seal ring and that has a concave groove that accommodates the seal ring formed on an inner peripheral surface thereof, and the base-side seal ring has a thermal expansion coefficient equal to or greater than that of the boss portion. It is preferable that it consists of the material which is.

In this case, the tip side sealing ring on which the second sealing end face is formed is made of a material suitable for contacting the first sealing end face of the first sealing ring as a contact partner, and the base side sealing ring is used as the tip part. It can be made of a material different from that of the side sealing ring. Therefore, the base side sealing ring is made of a material having a thermal expansion coefficient equal to or greater than that of the boss part, so that even if the temperature rises and the boss part expands in the radial direction, the base side sealing ring does not radiate in the radial direction. Can expand to the same level or higher.
If the second seal ring (base side seal ring) cannot expand in the radial direction more than the boss part, the seal ring is tightened in the radial direction to seal between the second seal ring (base side seal ring) and the boss part. The margin increases, the resistance when the second sealing ring including the base side sealing ring moves to the first sealing ring side increases, the movement of the second sealing ring is suppressed, and poor contact between the sealing end surfaces occurs. The sealing performance may be reduced. However, according to the configuration of the present invention, the base-side sealing ring can expand in the radial direction to the same level or more as the boss portion, and thus it is possible to prevent the deterioration of the sealing performance as described above.

Further, in this case, the seal ring is made of a material having a thermal expansion coefficient larger than that of the base-side sealing ring, and between the concave groove and the seal ring that is externally fitted to the boss portion and in a normal temperature state, A radial clearance is preferably formed.
According to the clearance, even if the seal ring expands and expands due to high temperature, the seal ring can prevent the concave groove of the base side seal ring from being pushed strongly radially outward. The movement of the second sealing ring including the base side sealing ring is not suppressed, and the sealing performance between the first sealing end surface and the second sealing end surface can be maintained.

  According to the present invention, even if the pressure of the fluid to be sealed is increased and the second sealing ring is distorted, the flatness of the entire second sealing end surface and the parallelism with respect to the counterpart first sealing end surface are reduced. Therefore, it is possible to maintain an appropriate contact state between the sealing end faces, and it is possible to maintain a sealing function.

It is a longitudinal cross-sectional view which shows one Embodiment of the sealing device provided with the contact-type mechanical seal of this invention. It is a longitudinal cross-sectional view of a 2nd mechanical seal. It is explanatory drawing explaining the principal part of a 2nd mechanical seal. It is a front view of a front part side sealing ring. It is a front view of the front part side sealing ring of other forms. It is a front view of the front part side sealing ring of other forms. It is explanatory drawing of the uneven | corrugated pattern of a sealing end surface, (a) has shown the outer peripheral side part, (b) has shown the radial direction intermediate part, (c) has shown the inner peripheral side part. It is explanatory drawing of a sealing ring.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing an embodiment of a sealing device provided with a contact type mechanical seal of the present invention. This sealing device is for partitioning the inside of the machine (right side in FIG. 1) and the outside of the machine (left side) of a rotary device such as a pump and a mixer, and sealing the fluid existing inside the machine.
The rotating machine includes a device casing 1 and a rotating shaft 2 provided coaxially with the inner peripheral surface of the device casing 1. A shaft seal casing 4 provided in the sealing device is fixed to the device casing 1 so as to be coaxial with the rotary shaft 2.

  The sealing device further includes a first mechanical seal 10 inside the machine and a second mechanical seal 20 outside the machine. These seals 10 and 20 are provided in an annular space 3 formed between the inner peripheral surface 4 a of the shaft seal casing 4 and the rotary shaft 2. The first mechanical seal 10 and the second mechanical seal 20 are provided side by side in the axial direction of the rotary shaft 2.

The first mechanical seal 10 includes an annular rotary retainer 11 attached to the inside of the sleeve 2a that is externally fitted and fixed to the rotary shaft 2, and a rotary seal ring 12 that is non-rotatably attached to the retainer 11 in the circumferential direction. An annular stationary retainer 13 fixed to the shaft seal casing 4, a stationary sealing ring 14 attached to the stationary retainer 13 so as not to rotate in the circumferential direction and to be movable in the axial direction, and a stationary sealing ring 14 And a spring 15 for pressing the rotary seal ring 12 side. The stationary seal ring 14 has a base side seal ring 14a and a front side seal ring 14b.
Then, when the sealing end face 16 of the rotary sealing ring 12 and the sealing end face 17 of the stationary sealing ring 14 are in contact with each other, a fluid area A which is the inside of the machine and an intermediate area B where a purge gas is discharged (described later). And the fluid existing in the fluid region A is sealed (primary sealing). The first mechanical seal 10 of the embodiment is a contact type mechanical seal (contact type dry contact seal).

The second mechanical seal 20 includes an annular rotary retainer 21 attached to the sleeve 2a, a rotary seal ring (first seal ring) 22 attached to the retainer 21 so as not to rotate in the circumferential direction, and a shaft seal casing. 4, an annular stationary side retainer 23 fixed to the stationary side retainer 23, a stationary sealing ring 24 (second sealing ring) 24 that is attached to the stationary side retainer 23 so as not to rotate in the circumferential direction and to be movable in the axial direction, and stationary sealing ring 24 And a spring 25 that presses the rotary seal ring 22 toward the rotary seal ring 22 side. The stationary sealing ring 24 has a front side sealing ring 24b and a base side sealing ring 24a.
As a result, the rotary sealing ring 22 rotates around the axis C with respect to the stationary sealing ring 24 as the rotary shaft 2 rotates.

  Then, the sealing end surface (first sealing end surface) 26 formed on the rotary sealing ring 22 and the sealing end surface (second sealing end surface) 27 formed on the base side sealing ring 24a come into contact with each other. The intermediate region B is separated from the atmospheric region H which is the outside of the machine, and the fluid leaking from the first mechanical seal 10, that is, the fluid existing in the intermediate region B is sealed (secondary sealing). The second mechanical seal 20 is a contact type mechanical seal (contact type dry contact seal).

  FIG. 2 is a longitudinal sectional view of the second mechanical seal 20. The rotary seal ring 22 is an annular member having a substantially square cross section that is fixed to the rotary shaft 2 via a sleeve 2 a and a rotary side retainer 21. The axial end surface facing the stationary seal ring 24 is a smooth sealed end surface 26 orthogonal to the axis C. A gap is provided between the outer peripheral surface of the rotary retainer 21 and the inner peripheral surface 4a of the shaft seal casing 4 on the outer side in the radial direction of the rotary seal ring 22, and an intermediate region B (described later). The flow of fluid is free between the inner side area K2 which is the front side of the stationary seal ring 24.

  The stationary side retainer 23 is an annular member, and includes a disc-shaped main body portion 23a fixed to the shaft seal portion casing 4, and a cylindrical boss portion extending in the axial direction from the inner peripheral side portion of the main body portion 23a. 23b and a cylindrical outer tube portion 23c extending in the axial direction from the main body portion 23a on the outer side in the radial direction than the boss portion 23b. The boss portion 23b is located radially inward of the stationary sealing ring 24 having the front side sealing ring 24b and the base side sealing ring 24a, and the front side sealing ring 24b and the base side sealing ring 24a It is guided so as to be movable toward the rotary seal ring 22 along the C direction.

FIG. 3 is an explanatory diagram for explaining a main part of the second mechanical seal 20. As described above, the stationary sealing ring 24 is divided into the front side sealing ring 24b and the base side sealing ring 24a in the axial direction and is a separate body. A sealing end surface 27 is formed on the axial end surface of the front-side sealing ring 24b.
A concave groove 29 for accommodating an O-ring 28 (ring seal) is formed at a corner of the inner peripheral surface of the base side sealing ring 24a. A side wall 29a of the concave groove 29 and a front side sealing ring facing the side wall 29a. The inner peripheral side wall 29b of 24b and the bottom wall 29c of the concave groove 29 constitute an accommodating portion that surrounds the O-ring 28 from three directions. The base side sealing ring 24 a has a square cross section except for the concave groove 29 portion for the O ring 28.
The O-ring 28 can simultaneously seal between the base-side sealing ring 24a and the boss 23b of the stationary retainer 23 and between the base-side sealing ring 24a and the front-side sealing ring 24b.
The base side sealing ring 24a is fitted around the boss portion 23b with a gap, and is attached to the main body portion 23a of the rotation side retainer 21 (see FIG. 2) via a spring 25.

  The front-side sealing ring 24 b has a main body 30 that is substantially square in cross section, and an annular portion 31 that extends radially outward from the outer periphery of the main body 30. An end face in the axial direction facing the rotary seal ring 22 in the front side seal ring 24 b is a smooth sealed end face 27 orthogonal to the axis C. A gap (throttle portion 35) is provided between the outer peripheral surface of the annular portion 31 and the inner peripheral surface of the outer cylindrical portion 23c on the outer side in the radial direction of the front-side sealing ring 24b. The flow of the fluid is free between an outboard side area K1 which is the base side and an inboard side area K2 which is the front side.

A plurality of concave portions 37 to be described later are formed in the annular portion 31 of the front side sealing ring 24b in the circumferential direction, and a pin 32 (see FIG. 1) extending in the axial direction from the stationary side retainer 23 By fitting in the concave portion 37, the front side sealing ring 24 b is not rotatable in the circumferential direction.
The base-side sealing ring 24a and the front-side sealing ring 24b are provided between the boss portion 23b and the outer cylinder portion 23c of the stationary side retainer 23, are limited in radial movement, and rotate in the circumferential direction. Although impossible, it is movable in the axial direction.

  A plurality of the springs 25 are provided at equal intervals in the circumferential direction. The spring 25 is compressed in the attached state, and the stationary sealing ring 24 is attached to the rotating sealing ring 22 side so as to press the sealing end surface 27 of the front side sealing ring 24 b against the sealing end surface 26 of the rotating sealing ring 22. It is fast. That is, the spring 25 pushes the base-side seal ring 24a in the axial direction, the base-side seal ring 24a pushes the front-side seal ring 24b in the axial direction via the O-ring 28, and the front-side seal ring 24b 22 is pressed. For this reason, the sealing end surface 27 of the front side sealing ring 24b and the sealing end surface 26 of the rotary sealing ring 22 are in surface contact to prevent the fluid in the region K2 connected to the intermediate region B from leaking to the atmosphere region H side. is doing.

The further leak prevention function which the 2nd mechanical seal 20 has is demonstrated.
In FIG. 2, a purge gas supply means (not shown) is connected to the shaft seal casing 4 and a supply passage 4b is formed for supplying purge gas to an outboard side region K1 on the back side of the front seal ring 24b. ing. Purge gas is supplied from the purge gas supply means to the outboard side region K1 through the supply path 4b. Further, a discharge passage 4c for discharging the purge gas from the machine inner side region K2 of the base side sealing ring 24 to the purge gas supply means side is formed. The purge gas is a gas that does not interfere even if it leaks into the fluid region A and the atmospheric region H, and can be, for example, nitrogen gas.
The purge gas supplied to the outboard area K1 passes through the throttle portion 35 and flows into the inboard side area K2, but pressure loss occurs due to passing through the throttle section 35, and the pressure of the purge gas in the inboard area K2 Is smaller than the pressure of the purge gas in the outboard side region K1.

An annular groove 33 is formed in the sealing end surface 27 of the front-side sealing ring 24b, and a communication path 34 that connects the annular groove 33 and the outboard side region K1 is formed. A plurality of communication paths 34 are formed at predetermined intervals (equal intervals) in the circumferential direction. For this reason, the purge gas can enter the annular groove 33.
Since the sealing state is secured by the surface contact between the sealing end surface 27 of the front side sealing ring 24 b and the sealing end surface 26 of the rotary sealing ring 22, the leakage of the purge gas from the annular concave groove 33 hardly occurs. For this reason, the internal pressure of the machine outside region K1 and the annular groove 33 is almost the same. As a result, the internal pressure of the annular groove 33 can be kept larger than the internal pressure of the machine inside area K2, and the mixed gas of the gas existing in the machine inside area K2 (intermediate area B) and the purge gas is annular. It is possible to prevent intrusion into the concave groove 33, that is, between the sealing surfaces of the second mechanical seal 20 (between the sealing end surfaces 26 and 27) and leak to the atmosphere region H side. Further, by supplying the purge gas to the annular groove 33, the sealed end surfaces 26 and 27 that are in sliding contact with each other can be cooled by the purge gas.

  The front-side seal ring 24 b is made of a material that is softer than the rotary seal ring 22. For example, the front side seal ring 24b is made of carbon (oil-impregnated carbon). The rotary seal ring 22 is made of a hard material, and examples of the hard material include ceramics such as WC and SiC, cemented carbide, and the like. Therefore, the front-side sealing ring 24 b of the stationary sealing ring 24 is configured to be more easily distorted than the rotary sealing ring 22 due to the pressure of the fluid to be sealed.

As shown in FIG. 3, the cross-sectional shape of the front-side sealing ring 24b (the cross-sectional shape on the plane passing through the axis C) does not have a symmetrical axis that passes through the centroid of the cross-section. It is. That is, the cross-sectional shape of the front-side sealing ring 24b is complicated and has a shape that is largely changed partially. On the other hand, the rotary seal ring 22 has a substantially square cross-sectional shape.
Therefore, the front-side seal ring 24b of the stationary seal ring 24 has a configuration that is more easily distorted than the rotary seal ring 22, that is, a configuration that easily causes a distortion that involves rotation around the centroid of the cross section. Yes.

For this reason, when the pressure of the fluid increases, the front-side seal ring 24b has a maximum strain due to the compressive force generated by the pressure compared to the rotary seal ring 22, and a locally large strain is generated in the circumferential direction. May occur discontinuously. As described above, when a large local distortion occurs discontinuously, the flatness at the sealing end surface 27 of the front side sealing ring 24b and the parallelism with respect to the sealing end surface 26 of the rotary sealing ring 22 are impaired, and the sealing performance is adversely affected. There is a risk of giving.
Therefore, in the present invention, when the pressure by the fluid acts on the surface portion of the front side sealing ring 24b other than the sealing end surface 27 and continuous in the circumferential direction, intensive strain is generated. The cross-section changing portions 37 are arranged evenly (at equal intervals) in the circumferential direction.

  FIG. 4 is a front view of the front-side sealing ring 24b. In this embodiment, the cross-section changing portion 37 is a concave portion 37a, and particularly, a concave portion 37a formed by cutting out from the outer peripheral surface 31a of the annular portion 31 toward the inner peripheral side. In this concave portion 37a, the cross-sectional shape is greatly changed compared to the portion adjacent to the concave portion 37a in the circumferential direction (the portion where the concave portion 37a is not formed), and accordingly, with the deformation of the front side seal ring 24b, Concentrated strain (concentrated stress) occurs. The concave portions 37a are arranged at equal intervals in the circumferential direction, and are formed at eight locations in FIG. Moreover, in this embodiment, the surface part (outer peripheral surface 31a) in which the recessed part 37a is formed becomes a pressure receiving part (part where the fluid pressure acts) in contact with the fluid that prevents leakage.

The shape, number, and arrangement of the concave portions 37a (cross-section changing portions 37) are such that the same or substantially the same concave / convex pattern forms a undulation waveform in the circumferential direction by controlling the distortion generated in the sealed end surface 27 by the pressure of the fluid. Is set.
That is, assuming that the front-side sealing ring 24b is equally divided into a plurality of divided portions S around the axis C (assuming that the front-side seal ring 24b is equally divided into N in the circumferential direction), the concave portion 37a formed in each divided portion S; The concave portions 37a formed in the divided portions S adjacent thereto are formed so as to have the same number, shape and arrangement. As a result, stress concentration occurs due to the notch effect of the recess 37a at equal intervals in the circumferential direction, and a intensive strain is positively generated in the formation portion of the recess 37a, as shown in FIG. Further, a concavo-convex pattern (uneven pattern portion 40a) formed on the sealed end surface portion of each divided portion S and a distorted uneven pattern (uneven pattern portion 40a) formed on the sealed end surface portion of the divided portion S adjacent thereto. ) Are the same or nearly the same. 7A and 7B are explanatory diagrams of the uneven pattern of the sealing end faces 26 and 27, where FIG. 7A shows the outer peripheral side portion, FIG. 7B shows the radial intermediate portion, and FIG. 7C shows the inner peripheral portion (FIG. 7). 7 shows the sealing end faces 26 and 27 apart from each other for the purpose of explanation).

  The number of divided portions S (equal fraction) N, that is, the number of concavo-convex patterns (continuous number) formed over the entire circumference of the sealing end surface 27 is such that the strength of the front side sealing ring 24b is sealed by forming the concave portion 37a. It is preferable to set as many as possible within a range that does not adversely affect the function. In the embodiment shown in FIG. 4, N = 8. However, as shown in FIG. 5, N = 16 or the like may be used.

Further, as shown in FIG. 8 (a), in order to bring the sealing end faces 26 and 27 into an appropriate contact state, the number, shape, and shape of the concave portions 37a (cross-section changing portions 37) formed in the respective divided portions S are determined. The arrangement is set according to conditions such as the degree of distortion to be controlled (distortion generated in the sealing end face 27 when the concave portion 37a is not formed), the cross-sectional shape of the front-side sealing ring 24b, and the like.
Furthermore, although the uneven | corrugated form in each uneven | corrugated pattern changes with the radial direction position of the front part side sealing ring 24b in relation to the position and shape of the recessed part 37a, the number, shape, and arrangement | positioning of the recessed part 37a are each It is preferable that the distortion amount in the radial direction of the pattern is set so that at least the inner peripheral side and the outer peripheral side of the sealed end surface 27 are the same or substantially the same.
That is, with reference to FIG. 7, the distortion amount f1 of the concave / convex pattern portion 40a on the outer peripheral side of the sealed end face 27 shown in FIG. 7 (a) and the concave / convex pattern portion 40c on the inner peripheral side shown in FIG. 7 (c). Further, as shown in FIG. 7B, the concave portion 37a (the concave portion 37a (so that the distortion amount f2 of the concave-convex pattern portion 40b in the radial intermediate portion is also the same). It is preferable to set the number, shape and arrangement of the cross-section changing portions 37).

Such a setting is realized by setting the radius of the first virtual circle to a predetermined value when the concave portions 37a are evenly arranged in the circumferential direction along the first virtual circle centered on the axis C. be able to.
Furthermore, a plurality of cross-section changing portions 37 may be provided in one divided portion S. For example, as shown in FIG. 5, a concave portion (cut) is formed along the first virtual circle R1 with the axis C as the center. (Notch) 37a is arranged at equal intervals in the circumferential direction, and another recess (hole) 37b is further arranged at equal intervals in the circumferential direction along the second imaginary line R2 having a diameter different from that of the first imaginary line R1. May be. In this case, the recess 37a along the first virtual circle R1 and the recess 37b along the second virtual circle R2 may have the same phase as shown in FIG.
As shown in FIG. 5, each divided portion S may be formed with a plurality of types of cross-section changing portions 37 having different shapes.

Thus, by setting the number, shape, and arrangement of the concave portions 37a so that the amount of distortion in the radial direction of each concave-convex pattern is at least the same or substantially the same on the inner peripheral side and the outer peripheral side of the sealed end surface 27. As shown in FIG. 8A, the sealed end faces 26 and 27 can be brought into an appropriate contact state.
As shown in FIG. 8B, the distortion is not uniform between the outer peripheral side and the inner peripheral side of the sealing end surface 27 of the stationary sealing ring 24, and the sealing end surface 27 is rotated by the rotation sealing ring. When the outer end of the sealing end surface 27 is distorted in the outwardly open state, the inner peripheral side end of the sealing end surface 27 is biased and strongly in contact with the mating sealing end surface 26. Further, as shown in FIG. 8C, when the sealing end surface 27 of the stationary sealing ring 24 is distorted in the inwardly open state, the outer peripheral side end of the sealing end surface 27 is strongly biased toward the counterpart sealing end surface 26. Contact. As a result, the stationary sealing ring 24 made of carbon may be damaged in a short period of time and may not be able to exhibit a good and stable sealing function over a long period of time.
However, if the number, shape, and arrangement of the concave portions 37a are set as described above, the concave / convex pattern can be controlled, and such problems can be solved.

As a specific example of the cross-sectional change part 37, it can be set as the recessed part which consists of a through hole and a counterbore hole (non-through hole) besides the recessed part which consists of a notch.
When a plurality of cross-section changing portions 37 are formed in each divided portion S, the cross-section changing portion 37 may be only a recess, only a counterbore, or both a recess and a counterbore.
Moreover, the cross-sectional change part 37 may be formed in the non-pressure receiving part which the fluid which prevents a leak does not contact | connect. For example, you may form in the internal peripheral surface of the front part side sealing ring 24b.
Furthermore, as shown in FIG. 7, in addition to the configuration in which the cross-section changing portion 37 is constituted by a single concave portion 37a as shown in FIG. 5, a concave portion group comprising a plurality of concave portions 37c provided in proximity to each other, can do. Thus, when setting it as a recessed part group, the shape of the recessed part 37c contained in the said recessed part group may each differ (not shown).

Further, in FIG. 1, a pin 32 extending in the axial direction from the stationary side retainer 23 is provided so that the front side sealing ring 24 b cannot rotate in the circumferential direction with respect to the stationary side retainer 23. Therefore, the pin 32 may be engaged with the concave portion 37a as the cross section changing portion 37 (see FIG. 4). That is, at least a part of the concave portion 37 a also serves as an engaging portion for preventing the rotation of the front side sealing ring 24 b by the pin 32.
In addition, you may provide the engaging part for rotation prevention of the front part side sealing ring 24b separately from the recessed part 37a as the cross-section change part 37. FIG. In this case, it is preferable to increase the number of the concave portions 37a as the cross-section changing portions 37 rather than the number of the engaging portions. This may cause the engaging portion to affect the distortion of the front seal ring 24b. In this case, in order to control the distortion by the cross-section changing portion 37 as described above, the number of the engaging portions is larger than the number of the engaging portions. This is because it is considered that a large number of cross-section changing portions 37 are required.

According to the second mechanical seal 20 according to the above embodiment, when the fluid is sealed, if distortion occurs in the front side seal ring 24b due to the pressure of the fluid, for example, in FIG. Concentrated strain (concentrated stress) can be positively generated in the cross-section changing portion 37 (concave portion 37a) provided on the outer peripheral surface 31a, and the cross-section changing portion 37 is evenly distributed in the circumferential direction. Since they are arranged, portions where intensive distortion occurs can be continued at equal intervals in the circumferential direction.
For this reason, the sealing end surface 27 of the front-side sealing ring 24b can be corrected to a surface in which the same or substantially the same uneven distortion pattern continues in the circumferential direction. That is, only a part of the sealing end surface 27 in the circumferential direction is prevented from being greatly deformed locally, and the flatness of the sealing end surface 27 as a whole and the parallelism of the mating rotary sealing ring 22 with the sealing end surface 26 are reduced. It can suppress that it falls.

In particular, when the cross-section of the front-side seal ring 24b has a shape as shown in FIG. 3 and fluid pressure acts from the outer peripheral surface side, the front-side seal ring 24b is compressed in the radial direction, and the recess 37a. In the case where is not formed, the front-side sealing ring 24b is deformed in a form as shown in FIG. In this case, contact marks are seen on the outer diameter portion of the sealing end face 26 of the rotary sealing ring 22.
However, by providing a defective portion such as the concave portion 37a as the cross-section changing portion 37 in the outer peripheral side portion (annular portion 31) of the front side seal ring 24b, concentrated stress (concentrated compressive stress) is generated in the defective portion. In addition, since the front-side sealing ring 24b is easily elastically deformed in the circumferential direction at the defect portion, the circumferential compressive stress that should act is released, and the outer-side portion of the front-side sealing ring 24b is released. It is considered that distortion (axial deformation) is reduced. For this reason, as shown to Fig.8 (a), the sealing end surfaces 26 and 27 are obtained an appropriate contact state.

Furthermore, the cross-section changing portion 37 positively generates intensive strain (concentrated stress) in the front-side sealing ring 24 b, thereby distributing the distortion generated in the entire front-side sealing ring 24 b to the entire sealing end surface 27. As a result, the maximum strain can be significantly reduced as compared with the case where the cross-section changing portion 37 is not formed.
As a result, the sealing end surface 27 of the front side sealing ring 24b, which is softer than the rotary sealing ring 22, is greatly deformed locally, and the deformation becomes discontinuous in the circumferential direction, so that the smoothness ( Flatness), parallelism with the sealing end face 26 as a counterpart, and concentricity can be prevented from being impaired, and the sealing function can be exhibited well and stably over a long period of time even under high pressure conditions.

  In FIG. 3, the stationary sealing ring 24 is divided into a base side sealing ring 24 a and a front side sealing ring 24 b and is a separate body. Therefore, the front side sealing ring 24 b constitutes the sealing end surface 27. Therefore, even if the front side sealing ring 24b is selected as such a material (made of carbon), the base side sealing ring 24a can be combined with the front side sealing ring 24b. Another material can be used. Therefore, the base side sealing ring 24 a can be made of a material having a thermal expansion coefficient (linear expansion coefficient) equal to or greater than that of the boss part 23 b of the stationary side retainer 23. Specifically, since the stationary side retainer 23 (boss portion 23b) is made of stainless steel, the base side sealing ring 24a is also made of the same stainless steel.

Thus, by making the base side sealing ring 24a made of the same stainless steel as the boss part 23b, even if the temperature rises in a high temperature use environment and the boss part 23b expands in the radial direction, the base side sealing ring 24a Can expand in the radial direction as well as the boss portion 23b.
If the base side sealing ring 24a cannot expand more than the boss part 23b in the radial direction, the radial tightening margin of the O-ring 28 that seals between the base side sealing ring 24a and the boss part 23b increases, Resistance when the side sealing ring 24a moves in the axial direction increases. For this reason, the movement (following with respect to the rotation sealing ring 22) of the stationary sealing ring 24 including the base side sealing ring 24a is suppressed, and the sealing performance may be deteriorated due to poor contact between the sealing end faces 26 and 27.
However, according to the configuration of the present invention, the base-side sealing ring 24a can expand in the radial direction in the same manner as the boss portion 23b, so that it is possible to prevent the deterioration of the sealing performance as described above.

Furthermore, since the O-ring 28 is made of rubber, the O-ring 28 has a thermal expansion coefficient larger than that of the base-side sealing ring 24a. For this reason, in a high-temperature environment, the boss portion 23b and the front-side sealing ring 24b expand in the radial direction in the same manner, and the O-ring 28 expands further in the radial direction.
In this case, it is conceivable that the interference between the O-ring 28 and the base-side sealing ring 24a becomes large. However, in order to prevent this, as shown in FIG. 3, the radially outer wall (bottom wall) 29c of the concave groove 29 formed on the inner peripheral surface of the base side sealing ring 24b, and the boss portion A radial clearance e is formed between the outer ring 23b and the O-ring 28 that is in a normal temperature state. That is, the concave groove 29 is formed so that the diameter D of the bottom wall 29c of the concave groove 29 is larger than the outer diameter d of the O-ring 28 that is fitted on the boss portion 23b and is in a normal temperature state (D> d). Is set.
According to this clearance e, even if the O-ring 28 expands and expands in diameter due to high temperature, the O-ring 28 can be prevented from pushing the concave groove 29 strongly outward in the radial direction. The axial movement of the stationary sealing ring 24 including the side sealing ring 24a is not suppressed, and the sealing performance between the sealing end surfaces 26 and 27 can be maintained.

According to the second mechanical seal 20 according to the above embodiment, in the environment where the fluid to be sealed is at a high temperature (for example, 170 ° C.) and a high pressure (for example, 4 MPa), the front side sealing ring 24b is changed by the pressure and temperature change of the fluid. Even if it is distorted, it is possible to prevent the flatness of the sealed end surface 27 as a whole and the parallelism with respect to the sealing end surface 26 as a counterpart from being lowered. For this reason, the sealing end surfaces 26 and 27 can be maintained in an appropriate contact state, the sealing function can be maintained, and fluid leakage can be prevented over a long period of time.
Moreover, since the sealing end surfaces 26 and 27 are in an appropriate contact state (the state shown in FIG. 8A) and are not in a biased contact state (the states shown in FIGS. 8B and 8C), the sealing end surfaces In 26 and 27, the occurrence of abnormal wear and the occurrence of abnormal heat generation can be prevented.

Further, in FIG. 1, the fluid region A is at a high pressure, and the second mechanical seal 20 needs to supplementally seal the fluid leaking from the first mechanical seal 10, so that it is equivalent to the first mechanical seal 10. Has sealing performance. Therefore, each of the configurations of the second mechanical seal 20 can be applied to the first mechanical seal 10.
Further, the contact type mechanical seal of the present invention is not limited to the illustrated form, but may be of another form within the scope of the present invention. For example, a contact-type mechanical seal (sealing device) can be applied to rotating devices such as compressors and blowers in addition to pumps and mixers, and can also be applied to rotating devices in the electronic and medical fields. . Further, the first mechanical seal 10 may be a non-contact type in which the sealing end surfaces are not in contact with each other.

2 Rotating shaft 3 Space 4 Shaft seal casing 4a Inner peripheral surface 22 Rotating seal ring (first seal ring)
23 stationary side retainer 23b boss 24 stationary sealing ring (second sealing ring)
24a Base side sealing ring (base side sealing ring)
24b Tip side seal ring (tip side seal ring)
25 Spring (elastic member)
26 Sealed end face (first sealed end face)
27 Sealed end face (second sealed end face)
28 O-ring (seal ring)
29 Concave groove 37 Cross section change part e Clearance

Claims (3)

A first sealing ring and a second sealing ring which are provided in an annular space formed between an inner peripheral surface of the casing and a rotary shaft coaxial with the inner peripheral surface, and which rotate relative to each other by rotation of the rotary shaft; The first sealing end surface of the first sealing ring and the second sealing end surface of the second sealing ring are in contact with each other to seal the fluid on one side in the axial direction of the space, and A contact type mechanical seal having a configuration in which the second sealing ring is more easily distorted than the first sealing ring by pressure;
Of the second sealing ring, other than the second sealing end face, cross-section changing portions that can cause intensive strain are arranged uniformly in the circumferential direction on the surface portion that is continuous in the circumferential direction. A contact-type mechanical seal. An annular retainer that is located radially inward of the second seal ring and has a cylindrical boss portion that guides the movement of the second seal ring toward the first seal ring, and is fixed to the casing; ,
An elastic member that biases the second sealing ring toward the first sealing ring and presses the second sealing end surface against the first sealing end surface;
A seal ring that is provided between the second seal ring and the boss portion and seals between the two;
Further comprising
The second sealing ring has a front side sealing ring in which the second sealing end surface is formed, and a concave groove that is separate from the front side sealing ring and accommodates the sealing ring is formed on the inner peripheral surface. And has a base side sealing ring
The contact-type mechanical seal according to claim 1, wherein the base-side sealing ring is made of a material having a thermal expansion coefficient equal to or greater than that of the boss portion. The seal ring is made of a material having a thermal expansion coefficient larger than that of the base side seal ring,
The contact-type mechanical seal according to claim 2, wherein a radial clearance is formed between the concave groove and the seal ring that is externally fitted to the boss portion and is in a normal temperature state.

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